WO2018198494A1 - All-solid-state battery - Google Patents

Abstract

The purpose of the present invention is to provide an all-solid-state battery which has a high discharge voltage due to a low negative electrode potential, and also has an increased discharge capacity, making it possible to obtain a high energy density. The all-solid-state battery comprises a solid-state electrolyte layer, a positive electrode layer, and a negative electrode layer. The all-solid-state battery is characterized in that: the solid-state electrolyte layer is interposed between the positive electrode layer and the negative electrode layer; at least one of the positive electrode layer or the negative electrode layer is bonded with the solid-state electrolyte layer by firing; each of the solid-state electrolyte layer, the positive electrode layer, and the negative electrode layer includes a lithium ion-conductive solid-state electrolyte; and, after firing and in a completely discharged state, the negative electrode layer includes (a) TiO2 and (b) LixTi2O4 (x = more than zero to 2).

Description

All solid battery

The present invention relates to an all-solid-state battery that has a high discharge voltage due to a low negative electrode potential and that can obtain a high energy density by having a higher discharge capacity.

In recent years, lithium ion secondary batteries having a high energy density and being chargeable / dischargeable have been widely used in applications such as electric vehicle power supplies and portable terminal power supplies.
Many of the lithium ion secondary batteries currently on the market generally use a liquid electrolyte (electrolytic solution) such as an organic solvent in order to have a high energy density. This electrolytic solution is used by dissolving a lithium salt in an aprotic organic solvent such as carbonate ester or cyclic ester.

However, in a lithium ion secondary battery using a liquid electrolyte (electrolytic solution), there is a risk that the electrolytic solution leaks. Moreover, the organic solvent etc. which are generally used for electrolyte solution are combustible substances, and there exists a problem that it is unpreferable on safety.

Therefore, it has been proposed to use a solid electrolyte instead of a liquid electrolyte (electrolytic solution) such as an organic solvent. In addition, a solid secondary battery in which a solid electrolyte is used as an electrolyte and the other components are also made of solid is being developed.

Japanese Patent Application Laid-Open No. 2007-258165 (hereinafter referred to as Patent Document 1) discloses an all solid state battery including a solid electrolyte that is a cationic conductor having a NASICON structure, a positive electrode active material containing polyphosphoric acid, and a negative electrode active material.
However, in this method, the inventors have confirmed that the potential of the negative electrode of the all-solid-state battery is high and a high energy density cannot be obtained.

Also, WO2012 / 008422 (hereinafter referred to as Patent Document 2) discloses an all-solid battery using a lithium ion conductor having a NASICON structure as a solid electrolyte and anatase-type titanium oxide as a negative electrode active material. In the method described in Patent Document 2, it has been confirmed that the negative electrode potential is lower than that in Patent Document 1. However, in the method described in Patent Document 2, the potential drop gradient until reaching the plateau region of the potential drop in the discharge capacity-potential curve is gentle, and the charge potential with respect to the positive electrode active material in the interval up to the plateau region is It has been confirmed by the inventors that the battery cannot be sufficiently raised, thereby reducing the discharge capacity of the battery, resulting in a lower energy density.

Although not an all-solid-state battery, Non-Patent Document 1 discloses a study of a lithium ion battery using anatase-type TiO ₂ as a negative electrode active material. According to Non-Patent Document 1, when anatase-type TiO ₂ is used as the negative electrode active material, the negative electrode active material has an orthorhombic Li _x Ti ₂ O ₄ (x = 0-1) is disclosed. It is disclosed that a lithium ion battery using orthorhombic Li _x Ti ₂ O ₄ (x = 0 to 1) has a high potential of Livs 1.8V.

JP2007-258165A WO2012 / 008422

The present invention solves the above-described problems, and provides an all-solid-state battery capable of obtaining a high energy density by having a high discharge voltage due to a low negative electrode potential and further having a high discharge capacity. Objective.

In order to solve the above-mentioned problems, the present inventors have conducted intensive test studies. As a result, Li ₄ Ti ₅ O ₁₂ , TiO ₂ , or LiTi ₂ O ₄ , As a lithium ion conductive solid electrolyte, an anatase type in which Li is slightly pre-doped in the negative electrode layer in a completely discharged state by preparing a glass electrolyte and a ceramic electrolyte or a glass ceramic electrolyte, and a conductive additive by mixing and firing. It was found that a mixed phase of TiO ₂ and Li _x Ti ₂ O ₄ (x = 0 to 2) was produced. Furthermore, it has been found that the above mixed phase becomes cubic Li _x Ti ₂ O ₄ (x = 0 more than 2) in a charged state. Further, the cubic Li _x Ti ₂ O ₄ (x = 0 to 2) has a lower potential than the orthorhombic Li _x Ti ₂ O ₄ (x = 0 to 1), resulting in an energy density. The present invention has been completed.
That is, according to the present invention, the following all solid state battery is provided.

(1) An all-solid battery including a solid electrolyte layer, a positive electrode layer, and a negative electrode layer,
The solid electrolyte layer is interposed between the positive electrode layer and the negative electrode layer, and at least one of the positive electrode layer or the negative electrode layer and the solid electrolyte layer are bonded by baking,
The solid electrolyte layer, the positive electrode layer, and the negative electrode layer all include a lithium ion conductive solid electrolyte,
The negative electrode layer is as follows:
(A) a negative electrode active material containing Li ₄ Ti ₅ O ₁₂ , TiO ₂ , or LiTi ₂ O ₄ ;
(B) glass electrolyte and (c) ceramic electrolyte or glass ceramic electrolyte,
An all solid state battery characterized in that it is obtained by sintering a material containing

(2) The glass electrolyte is 10% by mass to 30% by mass of Li ₂ O component, more than 0% by mass to 12% by mass of Al ₂ O ₃ component, and 40% by mass to 90% by mass on the oxide basis. % P ₂ O ₅ component and not including one or more selected from Y ₂ O ₃ component, Sc ₂ O ₃ component, ZrO ₂ component, CeO ₂ component and Sm ₂ O ₃ component (1 ) All-solid battery described.

(3) The all-solid-state battery according to (1) or (2), wherein the negative electrode layer contains TiO ₂ and Li _x Ti ₂ O ₄ (x = 0 to 2) after firing and in a completely discharged state.

(4) The all-solid-state battery according to any one of (1) to (3), wherein the negative electrode layer contains cubic Li _x Ti ₂ O ₄ (x = 0 to more than 2) after charging.

(5) An all-solid battery including a solid electrolyte layer, a positive electrode layer, and a negative electrode layer,
The solid electrolyte layer is interposed between the positive electrode layer and the negative electrode layer, and at least one of the positive electrode layer or the negative electrode layer and the solid electrolyte layer are bonded by baking,
The solid electrolyte layer, the positive electrode layer, and the negative electrode layer all include a lithium ion conductive solid electrolyte,
The negative electrode layer is in a fully discharged state after firing,
(A) TiO ₂ , and (b) Li _x Ti ₂ O ₄ (x = 0 more than 2)
All-solid-state battery characterized by including.

(6) The all-solid-state battery according to (5), wherein the negative electrode layer contains cubic Li _x Ti ₂ O ₄ (x = 0 to 2) after charging.

According to the present invention, the fired negative electrode layer includes a mixed phase of TiO ₂ and LiTi ₂ O ₄ (x = 0 to more than 2) pre-doped with Li, and the mixed phase is cubic in a charged state. By being Li _x Ti ₂ O ₄ (x = 0 more than 2), the all solid state battery of the present invention has a high discharge voltage due to a low negative electrode potential. Further, as shown in the result of the discharge measurement, due to the remarkably steep slope of the negative electrode potential drop until reaching the plateau region of the potential drop, it has a low negative electrode potential at the time of low discharge capacity. Therefore, the voltage and current capacity that can be effectively used as a battery are increased, and as a result, an all-solid battery having a high energy density can be obtained.

It is a partial schematic diagram explaining the structure of one Embodiment of the all-solid-state battery of this invention. FIG. 3 is a schematic view of an opening formed in sheets A to G produced in an example of the present invention. It is the result of the discharge measurement of Example 1, Example 2, and Comparative Example 1. FIG. It is a powder X-ray-diffraction measurement result of the charge depth of Example 1 of 0% (before charge). It is a powder X-ray-diffraction measurement result of the charge depth of Example 1 of 20%. It is a powder X-ray-diffraction measurement result of the charge depth of Example 1 of 50%. FIG. 7 is a graph of the abundance of TiO ₂ and LiTi ₂ O ₄ in the negative electrode layer obtained by powder X-ray diffraction measurement of FIGS. Is the result of the half-cell tests for the negative electrode layer in which the TiO ₂ or _Li 4 _Ti 5 _{O 12} as a negative electrode active material.

FIG. 1 shows an all-solid battery of the present invention. As shown in FIG. 1, the all solid state battery 1 of the present invention includes a solid electrolyte layer 2 and a positive electrode layer 3 and a negative electrode layer 4 provided at positions facing each other with the solid electrolyte layer 2 interposed therebetween. A laminate including the positive electrode layer 3, the negative electrode layer 4, and the solid electrolyte layer 2 is formed, and at least one of the positive electrode layer 3 or the negative electrode layer 4 and the solid electrolyte layer 2 are joined by firing.

Hereinafter, embodiments of the all-solid-state battery of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and may be implemented with appropriate modifications within the scope of the object of the present invention. can do. In addition, although description may be abbreviate | omitted suitably about the location where description overlaps, the meaning of invention is not limited.

The negative electrode layer in the all solid state battery of the present invention is preferably obtained by sintering a negative electrode active material, a glass electrolyte as a lithium ion conductive solid electrolyte and a ceramic electrolyte, or a material containing a glass ceramic electrolyte and a conductive additive. .
The positive electrode layer in the all solid state battery of the present invention is obtained by sintering a positive electrode active material, a glass electrolyte as a lithium ion conductive solid electrolyte, at least one of a ceramic electrolyte or a glass ceramic electrolyte, and a material containing a conductive additive. It is preferable.
The solid electrolyte layer in the all solid state battery of the present invention is preferably formed by sintering a material containing at least one of a glass electrolyte, a ceramic electrolyte, or a glass ceramic electrolyte as a lithium ion conductive solid electrolyte.

The glass electrolyte contained in any of the materials of the negative electrode layer, the positive electrode layer, and the solid electrolyte layer in the all solid state battery of the present invention will be described in detail below.

(Glass electrolyte)
The glass electrolyte used in the present invention has a basic composition of Li ₂ O—Al ₂ O ₃ —P ₂ O ₅ .
Unless otherwise specified, the content of each component contained in the glass electrolyte of the present invention is expressed in terms of mass% based on the oxide. Here, the “oxide equivalent composition” means that the oxide, composite salt, metal fluoride, etc. used as a raw material of the glass electrolyte are all decomposed and changed into oxides when melted, and then the generated oxides. It is the composition which described each component contained in a glass electrolyte by making a total mass into 100 mass%.
The glass electrolyte of the present invention is based on oxides,
10% by mass to 30% by mass of Li ₂ O component,
More than 0% by mass to 12% by mass of Al ₂ O ₃ component, and 40% by mass to 90% by mass of P ₂ O ₅ component, and Y ₂ O ₃ component, Sc ₂ O ₃ component, ZrO ₂ component, CeO _It does not contain one or more selected from _two components and Sm ₂ O ₃ components.

The Li ₂ O component is an essential component useful for imparting lithium ion conductivity by providing a Li ion carrier to the glass electrolyte. Further, by reducing the glass transition point and melting point and suppressing the firing temperature of the battery, side reactions can be suppressed and the discharge capacity can be increased. Therefore, the content of the Li ₂ O component is preferably 10% by mass or more, more preferably 15% by mass or more, still more preferably 18% by mass or more, and particularly preferably 20% by mass or more.
On the other hand, by making the content of the Li ₂ O component 30% by mass or less, it is possible to suppress a decrease in ion conductivity due to devitrification or crystallization of the glass when the molten glass raw material is cooled, and further, water resistance and the like. Increased chemical durability. Therefore, the content of the Li ₂ O component is preferably 30% by mass or less, more preferably 27% by mass or less, and still more preferably 24% by mass or less.
Li ₂ O component may be used to _{LiPO 3, Li 3 PO 4,} Li 2 CO 3, LiNO 3, LiF , etc. as raw materials.

When the Al ₂ O ₃ component is contained in an amount of more than 0% by mass, the lithium ion conductivity can be increased, the glass transition point and the melting point can be decreased, the side temperature can be suppressed by suppressing the firing temperature of the battery, and the discharge capacity can be increased. And weather resistance can be increased. Therefore, the content of the Al ₂ O ₃ component is preferably more than 0% by mass, more preferably 2% by mass or more, still more preferably 3% by mass or more, and further preferably 3.5% by mass or more.
On the other hand, by the content of the Al ₂ O ₃ component below 12 mass%, it is possible to suppress deterioration in ionic conductivity due to the crystallization of the glass component.
Therefore, the content of the Al ₂ O ₃ component is preferably 12% by mass or less, more preferably 8% by mass or less, and still more preferably 6% by mass or less.
As the Al ₂ O ₃ component, Al (PO ₃ ) ₃ , Al ₂ O ₃ , Al (NO ₃ ) ₃ .9H ₂ O, Al ₂ (CO ₃ ) ₃ or the like can be used as a raw material.

The P ₂ O ₅ component is an essential component useful for forming glass when it is contained in an amount of 40% by mass or more, and is a component that can increase the lithium ion conductivity and lower the glass transition point and the melting point. Furthermore, by suppressing the firing temperature of the battery, side reactions can be suppressed and the discharge capacity can be increased. Therefore, the content of the P ₂ O ₅ component is preferably 40% by mass or more, more preferably 50% by mass or more, still more preferably 60% by mass or more, and particularly preferably 70% by mass or more.
On the other hand, by setting the content of the P ₂ O ₅ component to 90% by mass or less, the concentration of Li ₂ O necessary for lithium ion conduction can be increased, and lithium ion conductivity can be increased.
Accordingly, the content of the P ₂ O ₅ component is preferably 90% by mass or less, more preferably 85% by mass or less, and still more preferably 80% by mass or less.
As the P ₂ O ₅ component, Li ₃ PO ₄ , LiPO ₃ , Al (PO ₃ ) ₃ , H ₃ PO _4, or the like can be used as a raw material.

When the positive electrode active material or negative electrode active material and the solid electrolyte are baked at a high temperature, Li and transition metals diffuse to cause an increase in internal resistance and a decrease in discharge capacity, and the solid electrolyte, positive electrode active material or negative electrode active material increase the charge / discharge capacity. Side reactions such as decomposition into materials that do not have occur. By using the above glass electrolyte, the glass electrolyte softens at a low temperature of about 600 ° C. to form an interface, and an all solid state battery can be configured at a low temperature, thereby suppressing the side reaction.

Hereinafter, the negative electrode layer, the positive electrode layer, or the solid electrolyte layer of the present invention will be described in detail.
(Negative electrode layer)
The negative electrode layer in the all solid state battery of the present invention is preferably obtained by sintering a negative electrode active material, a glass electrolyte as a lithium ion conductive solid electrolyte and a ceramic electrolyte, or a material containing a glass ceramic electrolyte and a conductive additive. .
As the negative electrode active material, a metal oxide, preferably a Ti oxide, more preferably Li ₄ Ti ₅ O ₁₂ , TiO ₂ or LiTi ₂ O ₄ may be used. TiO ₂ is particularly anatase type is preferable.
The content of the negative electrode active material with respect to the total mass of the negative electrode layer material is preferably 10% by mass to 50% by mass. In particular, when the content is 10% by mass or more, the battery capacity of the all solid state battery can be increased. Therefore, the content of the negative electrode active material is preferably 10% by mass or more, more preferably 15% by mass or more, and still more preferably 18% by mass or more. On the other hand, the ion conductivity of the electrode layer can be easily secured by setting the content to 50% by mass or less. Therefore, the content of the negative electrode active material is preferably 50% by mass or less, more preferably 40% by mass or less, and still more preferably 28% by mass or less.

When Li ₄ Ti ₅ O ₁₂ , TiO ₂ or LiTi ₂ O ₄ is used as the negative electrode active material, the decomposition reaction of the solid electrolyte can be suppressed by using the glass electrolyte of the present invention, and the internal resistance of the solid electrolyte can be kept low. .

When the content of the glass electrolyte with respect to the total mass of the negative electrode layer material is 2% by mass or more, an interface of lithium ion conductivity can be formed. The glass electrolyte is a component that increases the density of the negative electrode layer and increases the energy density per volume. Therefore, the content of the glass electrolyte is preferably 2% by mass or more, more preferably 3% by mass or more, still more preferably 4% by mass or more, and particularly preferably 5% by mass or more.
On the other hand, when the content of the glass electrolyte with respect to the total mass of the negative electrode layer material is 20% by mass or less, lithium resulting from an excessive presence of a glass electrolyte having a lower lithium ion conductivity than the ceramic electrolyte. A decrease in ionic conductivity can be suppressed. In addition, since the electron conduction in the negative electrode layer is formed by electron transfer caused by contact or bonding between the conductive assistants, if the contact between the conductive assistants is hindered by a glass electrolyte having no electron conductivity, the resistance of the electron conduction is reduced. Get higher. Therefore, it is possible to suppress a decrease in electron conductivity due to the excessive presence of a glass electrolyte having no electron conductivity. Therefore, the content of the glass electrolyte is preferably 20% by mass or less, more preferably 15% by mass or less, and still more preferably 10% by mass or less.

The ceramic electrolyte or glass ceramic electrolyte contained in the negative electrode layer material is preferably a lithium-containing phosphate compound having a NASICON structure. It is represented by the chemical formula Li _x M ₂ P ₃ O ₁₂ (X = 1 to 1.7). Here, M is one or more elements selected from the group consisting of Zr, Ti, Fe, Mn, Co, Ca, Mg, Sr, Y, La, Ge, Nb, and Al. Further, a part of P may be replaced with Si or B, and a part of O may be replaced with F, Cl or the like. For example, Li _1.2 Zr _1.85 Al _0.15 Si _0.05 P _2.95 O ₁₂ , Li _1.15 Zr _1.85 Al _0.1 Ti _0.05 Si _0.05 P _2.95 O ₁₂ etc. can be used. Further, materials having different compositions may be mixed or combined. The surface may be coated with a glass electrolyte or the like.

The content of the lithium conductive solid electrolyte with respect to the total mass of the negative electrode layer material is preferably 30% by mass to 80% by mass.
In particular, by setting the content to 30% by mass or more, it becomes easy to secure a migration path of lithium ions formed by the glass electrolyte, and thus it is possible to easily improve the charge / discharge characteristics and battery capacity of the battery. Therefore, the total content of the lithium conductive solid electrolyte in the electrode layer is preferably 30% by mass or more, more preferably 45% by mass or more, and further preferably 55% by mass or more.
On the other hand, since the content of the negative electrode active material contained in the negative electrode layer is increased by setting the content to 80% by mass or less, the energy density of the all-solid battery can be increased. Therefore, the content of the lithium conductive solid electrolyte in the negative electrode layer is preferably 75% by mass or less, more preferably 70% by mass or less, and further preferably 65% by mass or less.

In addition, as shown in Examples described later, the negative electrode layer of the present invention is pre-charged, that is, in a fully discharged state, Liat pre-doped anatase TiO ₂ and Li _x Ti ₂ O ₄ (X = 0). More than 2), and after charging, cubic Li _x Ti ₂ O ₄ (X = 0 more than 2).

When the negative electrode layer contains cubic Li _x Ti ₂ O ₄ (X = 0 to 2) after charging, it is possible to reduce the potential and obtain a battery with high energy density. Present glass electrolyte not, or in the state of Li absence in TiO ₂ anatase, _Li x _Ti 2 _O 4 of the TiO ₂ cubic after charging not (X = 0 ultra-2) and, on the negative electrode side As a result, the potential increases, the discharge voltage decreases, and the discharge capacity also decreases, so that the energy density of the battery decreases.

(Positive electrode layer)
The positive electrode layer in the all solid state battery of the present invention is obtained by sintering a positive electrode active material, a glass electrolyte as a lithium ion conductive solid electrolyte, at least one of a ceramic electrolyte or a glass ceramic electrolyte, and a material containing a conductive additive. It is preferable.
The kind of positive electrode active material of the said positive electrode layer is not limited. The positive electrode active material of the present invention is LiMPO ₄ having an olivine structure, and M is one or more of Fe, Co, Mn, and Ni, and a part thereof may be substituted with Al or the like. A part of P may be replaced with Si or B. A part of O may be substituted with F. Also, using LiMn ₂ O ₄ having a spinel structure, layered oxides LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ , LiNi _1/2 Mn _1/2 O ₂ , LiNiO ₂ , LiCoO _2, etc. Also good. The most preferred positive electrode active material has an olivine structure in which oxygen is strongly bonded to phosphorus because the discharge capacity decreases when oxygen is released by reacting with the solid electrolyte during firing. Next, a preferable positive electrode active material is LiMn ₂ O ₄ having a spinel structure in order, and then the layered oxide.
The content of the positive electrode active material with respect to the total mass of the positive electrode layer material is preferably 10% by mass to 50% by mass. In particular, when the content is 10% by mass or more, the battery capacity of the all solid state battery can be increased. Therefore, the content of the positive electrode active material is preferably 10% by mass or more, more preferably 18% by mass or more. On the other hand, the ion conductivity of the electrode layer can be easily secured by setting the content to 50% by mass or less. Therefore, the content of the positive electrode active material is preferably 50% by mass or less, more preferably 35% by mass or less.

When the content of the glass electrolyte with respect to the total mass of the positive electrode layer material is 2% by mass or more, a lithium ion conductive interface can be formed. The glass electrolyte is a component that increases the density of the positive electrode layer and increases the energy density per volume. Therefore, the content of the glass electrolyte is preferably 2% by mass or more, more preferably 3% by mass or more, still more preferably 4% by mass or more, and particularly preferably 5% by mass or more.
On the other hand, when the content of the glass electrolyte with respect to the total mass of the positive electrode layer material is 20% by mass or less, lithium resulting from excessive presence of a glass electrolyte having a lower lithium ion conductivity than the ceramic electrolyte. A decrease in ionic conductivity can be suppressed. In addition, since the electron conduction in the negative electrode layer is formed by electron transfer caused by contact or bonding between the conductive assistants, if the contact between the conductive assistants is hindered by a glass electrolyte having no electron conductivity, the resistance of the electron conduction is reduced. Get higher. Therefore, it is possible to suppress a decrease in electron conductivity due to the excessive presence of a glass electrolyte having no electron conductivity. Therefore, the content of the glass electrolyte is preferably 20% by mass or less, more preferably 15% by mass or less, and still more preferably 10% by mass or less.

The ceramic electrolyte or glass ceramic electrolyte of the positive electrode layer material of the present invention is preferably a lithium-containing phosphate compound having a NASICON type structure. Its chemical formula is represented by Li _x M ₂ P ₃ O ₁₂ (X = 1 to 1.7). Here, M is one or more elements selected from the group consisting of Zr, Ti, Fe, Mn, Co, Ca, Mg, Sr, Y, La, Ge, Nb, and Al. Further, a part of P may be replaced with Si or B, and a part of O may be replaced with F, Cl or the like. For example, Li _1.15 Ti _1.85 Al _0.15 Si _0.05 P _2.95 O ₁₂ , Li _1.2 Ti _1.8 Al _0.1 Ge _0.1 Si _0.05 P _2.95 O ₁₂ etc. can be used. Further, materials having different compositions may be mixed or combined. The surface may be coated with a glass electrolyte or the like. Alternatively, glass ceramics that precipitate a crystal phase of a lithium-containing phosphate compound having a NASICON structure by heat treatment may be used. Here, the blending ratio of Li ₂ O in the glass ceramic is preferably 8% by mass or less in terms of oxide.

The content of the lithium conductive solid electrolyte is preferably 30% by mass to 80% by mass with respect to the total mass of the positive electrode layer material.
In particular, by setting the content to 30% by mass or more, it becomes easy to secure a migration path of lithium ions formed by the glass electrolyte, and thus it is possible to easily improve the charge / discharge characteristics and battery capacity of the battery. Therefore, the total content of the lithium conductive solid electrolyte in the electrode layer is preferably 30% by mass or more, more preferably 45% by mass or more, and further preferably 55% by mass or more.
On the other hand, since the content of the positive electrode active material contained in the positive electrode layer is increased by setting the content to 80% by mass or less, the energy density of the all solid state battery can be increased. Therefore, the content of the lithium conductive solid electrolyte in the positive electrode layer is preferably 75% by mass or less, more preferably 70% by mass or less, and further preferably 65% by mass or less.

(Solid electrolyte layer)
The solid electrolyte layer in the all solid state battery of the present invention is preferably formed by sintering a material containing at least one of a glass electrolyte, a ceramic electrolyte, or a glass ceramic electrolyte as a solid electrolyte.

When the content of the glass electrolyte with respect to the total mass of the solid electrolyte layer material is 3% by mass or more, the glass electrolyte spreads over the ceramic electrolyte interface, and the ionic conductivity of the solid electrolyte layer can be increased. Further, since the density of the solid electrolyte layer can be increased, the strength can be increased. When it is less than 3% by mass, the ionic conductivity of the solid electrolyte layer cannot be increased. Therefore, the content of the glass electrolyte in the solid electrolyte layer is preferably 3% by mass or more, more preferably 4% by mass or more, still more preferably 4.5% by mass or more, and particularly preferably 5% by mass or more.
On the other hand, when the content of the glass electrolyte exceeds 15% by mass, the thickness of the glass electrolyte that connects the ceramic electrolytes increases, and the distance that lithium ions pass through the glass electrolyte increases. The influence of the conductivity of the glass electrolyte having a conductivity lower than that of the ceramic electrolyte is increased, and as a result, the ionic conductivity is lowered. Then, the fall of the above ionic conductivity can be prevented by making content of the said glass electrolyte into 15 mass% or less. Therefore, the content of the glass electrolyte is preferably 15% by mass or less, more preferably 12% by mass or less, and still more preferably 9% by mass or less.

The ceramic electrolyte or glass ceramic electrolyte contained in the solid electrolyte layer material is preferably a lithium-containing phosphate compound having a NASICON structure. It is represented by the chemical formula Li _x M ₂ P ₃ O ₁₂ (X = 1 to 1.7). Here, M is one or more elements selected from the group consisting of Zr, Ti, Fe, Mn, Co, Ca, Mg, Sr, Y, La, Ge, Nb, and Al. Further, a part of P may be replaced with Si or B, and a part of O may be replaced with F, Cl or the like. For example, Li _1.2 Zr _1.85 Al _0.15 Si _0.05 P _2.95 O ₁₂ , Li _1.15 Zr _1.85 Al _0.1 Ti _0.05 Si _0.05 P _2.95 O ₁₂ etc. can be used. Further, materials having different compositions may be mixed or combined. The surface may be coated with a glass electrolyte or the like.

The content of the lithium ion conductive solid electrolyte is preferably 80% by mass or more with respect to the total mass of the solid electrolyte layer material. Thereby, since the path | route which lithium ion conducts in a solid electrolyte layer becomes easy to be formed, the lithium ion conductivity of a solid electrolyte layer can be improved more.
On the other hand, the upper limit of the content of the lithium ion conductive solid electrolyte is not particularly limited, and may be 100% by mass.

(Conductive aid)
The negative electrode layer material and the positive electrode layer material may include a conductive additive. The conductive aid according to the present invention may be based on carbon materials such as carbon black, flaky graphite, graphene, carbon nanotubes, etc., but metal such as Ni, Co, Fe, Al, Pd, Cu, Ag or alloy fine particles thereof. May be mixed.

When the content of the conductive auxiliary in the negative electrode layer material or the positive electrode layer material is 3% by mass or more, it can form an electron conductive interface for transferring electrons from the electrode active material. The conductive auxiliary agent is a component that forms an electron conductive phase that guides the transferred electrons to the outside and reduces the resistance of the battery. When the content is 3% by mass or more, the lateral resistance of the negative electrode layer or the positive electrode layer can be reduced, the charge voltage can be reduced, and the discharge voltage can be increased. Therefore, the content of the conductive assistant is preferably 3% by mass or more, more preferably 4% by mass or more, still more preferably 5% by mass or more, and particularly preferably 6% by mass or more.
On the other hand, the content of the conductive additive with respect to the total mass of the negative electrode layer material or the positive electrode layer material is 20% by mass or less, thereby suppressing an increase in ion conduction resistance in the negative electrode layer or the positive electrode layer. . Further, by suppressing the use of a bulky carbon material, the density of the negative electrode layer and the positive electrode layer can be increased, and a decrease in volume energy density can be suppressed. Therefore, the content of the conductive assistant is preferably 20% by mass or less, more preferably 17% by mass or less, and still more preferably 13% by mass or less.

The all solid state battery of the present invention is manufactured as follows as an example.
It is preferable that at least one of the positive electrode layer, the negative electrode layer, or the solid electrolyte layer is prepared in the form of a green sheet, laminated to form a laminated body, and bonded by firing the laminated body. By firing, it is possible to produce an all-solid battery at low cost. Prior to firing the laminate, the laminate may be pressure fired after degreasing. In this case, the interface formation becomes better and the internal resistance of the battery is lowered, so that it is preferable to the case of only firing.

<Preparation of all-solid battery>
Hereinafter, a method for producing the all solid state battery of the present invention will be described.

Prepare electrode active material powder and solid electrolyte powder for negative electrode and positive electrode. Next, a slurry of the solid electrolyte layer, the positive electrode layer, and the negative electrode layer is prepared. Next, a slurry for each of the solid electrolyte layer, the positive electrode layer, and the negative electrode layer is formed to produce a green sheet. Next, a pattern is formed on the solid electrolyte layer, the positive electrode layer, and the negative electrode layer as necessary using a laser processing machine, a cutting machine, or a screen printing machine. Next, the green sheets of the solid electrolyte layer, the positive electrode layer, and the negative electrode layer are laminated to form a laminate. Next, the laminate is degreased. Degreasing removes organic components such as binder and dispersant in the laminate. Next, a heat treatment after pressurization is performed on the laminate. The solid electrolyte layer, the positive electrode layer, and the negative electrode layer are joined by the pressure treatment and the heat treatment. If necessary, the outer periphery is cold worked to remove the short-circuit portion. Finally, the fired laminate is bonded to an external terminal such as copper foil or aluminum foil using carbon paper or carbon paste. The sealing method is not particularly limited, but the outside atmosphere is simply blocked using an aluminum laminate film, resin, ceramics, glass or the like.

The method for forming the green sheet is not particularly limited, but a dam coater, a die coater, a comma coater, screen printing, or the like can be used. The method for laminating the green sheets is not particularly limited, but the green sheets can be formed using a hot press, a hot isostatic press (HIP), a cold isostatic press (CIP), a hydrostatic press (WIP), or the like. Can be stacked.

A slurry for forming a green sheet is prepared by wet-mixing an organic binder in which a polymer material is dissolved in a solvent, and a positive electrode active material powder, a negative electrode active material powder, a solid electrolyte powder, or a conductive additive powder. Specifically, a ball mill method, a viscomill method, or the like can be used. On the other hand, a wet mixing method that does not use media may be used, and a sand mill method, a high-pressure homogenizer method, a kneader dispersion method, or the like can be used. As the kind of the organic binder, acrylic is preferable because of a low degreasing temperature.

The slurry may contain a plasticizer. The kind of the plasticizer is not particularly limited, but phthalic acid esters such as dioctyl adipate and dioctyl phthalate may be used.

In the firing or degreasing step, the temperature and atmosphere are not particularly limited, but it is preferably performed at a temperature and atmosphere in which the electrode active material is not altered, the conductive auxiliary agent is not burned out, and the binder used for sheet forming is burned out. Specifically, it is preferably carried out at 250 ° C. to 700 ° C., preferably 300 ° C. to 650 ° C. using either air or nitrogen or both.

Next, examples of the present invention will be specifically described. In addition, the Example shown below is an example, This invention is not limited to the following Example, It can change arbitrarily in the range which does not impair the effect of the all-solid-state battery of this invention.
Using the positive electrode slurry, the negative electrode slurry, and the solid electrolyte slurry having the composition shown in Table 1, all-solid batteries of Examples 1 to 3 and Comparative Examples 1 to 2 were produced.
The all solid state battery of the present invention was produced by the following procedure.

<Preparation of glass electrolyte>
Li ₂ O—Al ₂ O ₃ —P ₂ O ₅ glass was prepared as a glass electrolyte. After the raw materials are weighed and uniformly mixed so as to contain 20% by mass of Li ₂ O, 4.5% by mass of Al ₂ O ₃ and 75.5% by mass of P ₂ O ₅ with an oxide reference composition The mixture was put into a crucible and melted at 1250 ° C. The molten glass was cast into water to prepare a glass electrolyte. The electrolyte was pulverized to a 106 μm mesh pass using a stamp mill, and then pulverized to a mean particle size of 1 μm or less using a wet planetary ball mill to obtain a glass electrolyte (hereinafter, this glass electrolyte is referred to as LIGAl9).

<Preparation of ceramic electrolyte>
Li _1.2 Al _0.15 Zr _1.85 Si _0.05 P _2.95 O ₁₂ was prepared as a ceramic electrolyte used for the negative electrode layer and the solid electrolyte layer. LiPO ₃ , ZrO ₂ , Al (PO ₃ ) ₃ , and SiO ₂ powders as raw materials and an H ₃ PO ₄ solution were mixed in a stoichiometric ratio, and then fired on a platinum plate at 1400 ° C. for 1 hour. The fired mixture of raw materials was pulverized to 106 μm or less by a stamp mill and pulverized to 1 μm or less by a wet planetary ball mill to obtain a ceramic electrolyte (hereinafter, this ceramic electrolyte is referred to as LAZP12).

As the glass ceramic electrolyte used for the positive electrode layer, a lithium ion conductive glass ceramic (LICGC (trademark)) manufactured by OHARA Inc. having an average particle diameter of 1 μm was used.

<Preparation of positive electrode slurry, negative electrode slurry and solid electrolyte slurry>

Table 1

The positive electrode slurry is a ratio shown in Table 1, LiLiPO ₄ (made by Hosen Co., Ltd.) as a positive electrode active material, glass electrolyte, glass ceramic electrolyte, and acetylene black (made by Electrochemical Industry Co., Ltd.) as a conductive additive. Denka Black (trade name)), flaky graphite (manufactured by Nippon Graphite Industry Co., Ltd.) and carbon nanotubes (manufactured by Sigma Aldrich) are added, and an acrylic polymer (Oricox 2427 (trade name), manufactured by Kyoeisha Chemical Co., Ltd.) is used as a binder. ), Di-2-ethylhexyl sebacate (DOS, manufactured by Ito Oil Co., Ltd.) as a plasticizer, BYK180 (manufactured by BYK-Chemie) as a polymeric dispersant, 1-propanol (Wako Pure Chemical Industries) as a solvent and a wetting material Silicone-containing oligomer (Polyflow KL-100, Kyoeisha) It was prepared by mixing in a ball mill with the addition of Co., Ltd.).
The negative electrode slurry is the ratio shown in Table 1, Li ₄ Ti ₅ O ₁₂ (manufactured by Titanium Industry Co., Ltd.) as the negative electrode active material, and acetylene black and flakes, which are the same as the positive electrode slurry as the glass electrolyte and ceramic electrolyte, and the conductive additive. Graphite and carbon nanotubes were added, and the same binder, plasticizer, dispersant, solvent and wetting material as the positive electrode slurry were further added and mixed by a ball mill.
The solid electrolyte slurry was prepared by adding the same binder, plasticizer, dispersant, solvent and wetting material as the positive electrode slurry to the glass electrolyte and the ceramic electrolyte and mixing them with a ball mill at the ratio shown in Table 1.

<Production of sheet>
The positive electrode slurry, the negative electrode slurry, and the solid electrolyte slurry prepared in the ratios shown in Table 1 are simultaneously applied to a base material made of PET having been subjected to a release treatment with a gap of 400 μm using a coating machine, and dried simultaneously. Drying was performed at a temperature of 110 ° C. to prepare a sheet having a thickness of 80 μm, a width of 20 cm, and a length of 5 m, and the sheet was cut into a 12 cm square to prepare a positive electrode sheet, a negative electrode sheet, and an electrolyte sheet.

<Green sheet processing, lamination, heat treatment>
Among them, the positive electrode sheet and the negative electrode sheet were irradiated with laser using a laser processing machine (manufactured by Panasonic Electric Works SUNX Co., Ltd., model number LPV-15U) to form an opening having a circular opening with a diameter of 1.2 mm. As shown in FIG. 2C, seven sheets of positive sheets with openings formed as sheets C were prepared, and seven sheets of negative sheets with openings formed as sheets A as shown in FIG. At this time, the positive electrode sheet and the negative electrode sheet were formed with openings at different positions. Further, as shown in FIG. 2D, one sheet of positive electrode sheet not forming an opening is prepared as a sheet D, and one sheet of negative electrode without opening is prepared as a sheet B as shown in FIG. did.
On the other hand, the solid electrolyte sheet is irradiated with laser using a laser processing machine, and an opening having a circular opening with a diameter of 0.8 mm is provided at a position overlapping with the center of at least one opening of the positive electrode sheet and the negative electrode sheet. Part was formed. At this time, as shown in FIG. 2F, one solid electrolyte sheet having an opening formed only at a position overlapping with the center of the opening of the positive electrode sheet is prepared as a sheet G, as shown in FIG. A solid electrolyte sheet having an opening formed only at a position overlapping with the center of the opening of the negative electrode sheet was prepared as a sheet F, and a solid electrolyte sheet having openings formed at both positions as shown in FIG. 13 sheets were prepared as sheet E.
A schematic diagram of the openings formed in the sheets A to G is shown in FIG.

Subsequently, the positive electrode sheet, the positive electrode sheet, the solid electrolyte sheet, the negative electrode sheet, the solid electrolyte sheet, and the positive electrode sheet were alternately stacked in this order using a single wafer type laminator (manufactured by Alpha System Co., Ltd.). More specifically, after the sheet D, the sheet F, the sheet A, the sheet E, the sheet C, and the sheet C are sequentially stacked, the sheet E, the sheet A, the sheet E, the sheet C, and the sheet C are repeated six times in this order. After that, the sheet G and the sheet B were sequentially laminated. At this time, the opening at the common position of the two positive electrode sheets and the opening at the solid electrolyte sheet adjacent to the opening are overlapped, and the opening of the negative electrode sheet and the solid electrolyte sheet adjacent thereto are present. The openings were overlapped.
At this time, the outer dimension of the sheet after the release treatment was set to 15 cm square, temporary lamination was performed every time each layer was laminated, and finally, two-stage pressing was performed as the main lamination. Temporary lamination was performed at a press pressure of 100 kPa by heating the laminate to 40 ° C. Next, vacuum deaeration was performed to remove bubbles in the sheet. Thereafter, the main laminate was heated to 55 ° C., and a sheet laminate was obtained at a press pressure of 250 kPa.

The sheet laminate was cut out at a diameter of 11 mm and degreased under a nitrogen atmosphere. Next, the upper mold was placed in a mold and heated to 600 ° C. while applying a pressure of 2000 kg / cm ² with a hydraulic press. After reaching 600 ° C., the pressure was released and the mixture was allowed to cool to room temperature. An outer periphery of 0.75 mm was polished with a # 800 grindstone to obtain a laminated all solid battery having a diameter of 9.5 mm, a thickness of 0.5 mm, and a weight of 82 mg. Each sheet thickness and the layers each density ratio obtained when burned its own thickness ratio observed by (positive electrode layer, negative electrode layer, both the solid electrolyte layer 2.3 g / cm ³⁾ and the secondary electron image observed The mass of the positive electrode active material and the negative electrode active material per cell calculated from the above was 12 mg. The diameter was evaluated using a digital caliper, the thickness was a digital micrometer, and an electronic balance capable of weighing up to 0.1 mg in mass.

(Example 2)
In Example 2, TiO ₂ which is tetragonal (anatase type) was used instead of Li ₄ Ti ₅ O ₁₂ used as the negative electrode active material of the negative electrode layer in Example 1. Other manufacturing conditions were the same as in Example 1, and a stacked all-solid battery was manufactured.

(Example 3)
In Example 3, in place of Li ₄ Ti ₅ O ₁₂ used as the negative electrode active material of the negative electrode layer in Example 1, cubic LiTi ₂ O ₄ (spinel structure) was used. Other manufacturing conditions were the same as in Example 1, and a stacked all-solid battery was manufactured.

(Comparative Example 1)
In Comparative Example 1, using TiO ₂ which is tetragonal in place of _Li 4 _Ti 5 _{O 12} was used as a negative electrode active material of the negative electrode layer in Example 2 (anatase). In order to consider the effect due to the presence of the glass electrolyte, the negative electrode layer was prepared without using the glass electrolyte as a comparison. Other manufacturing conditions were the same as in Example 1, and a stacked all-solid battery was manufactured.

(Comparative Example 2)
In Comparative Example 2, TiO ₂ which is tetragonal (anatase type) was used in place of Li ₄ Ti ₅ O ₁₂ used as the negative electrode active material of the negative electrode layer in Example 1. A laminated all-solid battery is fired at a firing temperature (500 ° C.) that is 100 ° C. lower than that of Example 1 so that the Li-containing component does not diffuse from the glass electrolyte or the ceramic electrolyte. Was made.

<Charge / discharge test>
In order to evaluate the characteristics of the battery, the charge / discharge test was conducted by joining a copper foil to the negative electrode surface of the laminated all-solid battery fabricated in Examples 1 to 3 and Comparative Examples 1 to 2, and an aluminum foil to the positive electrode surface. I went. Bonding was performed by applying a carbon paste to carbon paper, sandwiching it between the copper foil and aluminum foil and the cell, and firing in a dry room having a dew point of −50 ° C. After firing, the outside air was blocked by packaging with an aluminum laminate film in a dry room. About the sample which implements X-ray-diffraction measurement, the positive electrode and the aluminum foil and the negative electrode and the copper foil were electrically joined only by the crimping | compression-bonding with a vacuum pack, without using carbon paper and a carbon paste.
In addition, calculation of energy density used only the mass of the all-solid-state battery, and did not include aluminum foil, copper foil, carbon paper and paste, and aluminum laminate film.
The charge / discharge test was carried out by discharging at 50 μA after CC charging to 3 V at 50 μA at room temperature. The discharge cutoff was 0.1V. For all-solid-state cell fabricated the negative electrode active material with Li ₄ Ti ₅ O ₁₂ Example 1 Example 2 and Comparative Example 1 was used anatase TiO ₂ in the all-solid-state battery and the negative electrode active material was prepared by using The discharge characteristic measurement results are shown in FIG. As shown in Table 2, in the all solid state battery manufactured in Comparative Example 1 using anatase type TiO ₂ as the negative electrode active material and the negative electrode layer does not contain a glass electrolyte, the average operating voltage is 1194 mV, the discharge capacity is 85. It was 0.7 mAh / g and the energy density was 16.6 Wh / kg. On the other hand, in the all-solid-state battery manufactured in Example 1, the average operating voltage is 1480 mV, the discharge capacity is 140.3 mAh / g, and the energy density is 33.7 Wh / kg, which is the highest. Compared with the all-solid-state battery produced in Comparative Example 1, the point was greatly improved. In particular, the high average operating voltage of the all solid state battery produced in Example 1 is that the all solid state battery produced in Example 1 is operating at a higher potential than the all solid state battery of Comparative Example 1. showed that. In addition, the all solid state batteries produced in Example 2 and Example 3 both have higher discharge capacity, average operating voltage and energy density than the all solid state batteries produced in Comparative Example 1 and Comparative Example 2. confirmed.
Table 2 Results of charge / discharge test of all-solid battery of the present invention and presence of Li in negative electrode layer after firing

<X-ray diffraction>
The obtained laminated all solid state batteries of Examples 1 to 3 and Comparative Examples 1 and 2 were confirmed to have a crystalline phase by X-ray diffraction measurement. The X-ray diffractometer was X'Pert PRO MPD (Spectris), the target was Cu, the X-ray tube current was 40 mA, and the X-ray tube voltage was 45 kV. The scanning range was 2θ = 10.0-90.0 °. The detector was a semiconductor detector and the scanning time was 30 minutes or longer.
As samples, three samples having a diameter of 9.5 mm and a thickness of 0.5 mm were prepared, and the negative electrode side surface was measured. An aluminum laminate pack was used to charge, but was evaluated within 30 minutes after release from the laminate pack. In order to avoid the crystal structure change due to the discharge due to the short circuit, the sample in which the short circuit behavior was not observed was evaluated within 1 hour after the charge.
The X-ray diffraction measurement results at a charging depth of 0% (before charging), a charging depth of 20% and a charging depth of 50% are shown in FIGS. The strongest line of TiO ₂ near 2θ = 25 ° is indicated by ●, and the strongest line of LiTi ₂ O ₄ is indicated by ◆. Evaluation was made for three places of 0% charging depth (before charging), 20% charging depth, and 50% charging depth. FIG. 7 shows the results of arranging the strengths of the strongest lines of TiO ₂ (JCPDS 01-075-2547) near 2θ = 25 ° and LiTi ₂ O ₄ (JCPDS 01-082-2318) of cubic crystal around 2θ = 18 °. Indicated. From FIG. 7, it was confirmed that TiO ₂ decreased and LiTi ₂ O ₄ increased as the charging progressed. In the all solid state battery of Example 1 of the present invention, cubic Li ₄ Ti ₅ O ₁₂ used as the negative electrode active material of the negative electrode layer material becomes tetragonal (anatase type) TiO ₂ by the firing reaction, and the above TiO _{2 2,} it was confirmed that became LiTi ₂ O ₄ of a cubic with the progress of charging.
The chemical change is represented by the following chemical reaction formula.

(Baking reaction of negative electrode active material Li ₄ Ti ₅ O ₁₂ )
Li ₄ Ti ₅ O ₁₂ ⇒3.5TiO ₂ (Li minor content) + 0.5LiTi ₂ O ₄ + 3.5Li (solid solution in solid electrolyte) + O ₂

(Reaction that occurs in the negative electrode layer by charging)
3.5TiO ₂ (containing a small amount of Li) + 0.5LiTi ₂ O ₄ + 0.5Li ⁺ ⇒3TiO ₂ + LiTi ₂ O ₄

<Li concentration analysis>
In order to confirm more locally the relationship between the Li concentration in the negative electrode layer and the crystal structure of the all-solid-state battery of the present invention, the all-solid-state batteries of Examples 1 to 3 and Comparative Examples 1 and 2 were embedded in resin, and cryo-FIB was used. Samples of the flakes were prepared, STEM-ABF images and STEM-HAADF images were analyzed using an analytical electron microscope, electron beam analysis, and Li concentration analysis by electron energy loss spectroscopy (EELS) at the obtained site. The analytical electron microscope used was JEM-ARM200F (manufactured by JEOL Ltd.), the EELS spectrometer was QuantumER (manufactured by GATAN), the measurement conditions were 200 kV, and the EELS point analysis was performed for an acquisition time of 0.02 seconds or more.
The results obtained are shown in Table 2. In the all solid state battery produced in Example 1, the presence of Li was confirmed in the anatase TiO ₂ . The same analysis was performed for the all solid state batteries produced in Example 2 and Example 3 and the all solid state batteries produced in Comparative Example 1 and Example 2. In all the solid state batteries produced in Examples 1 to 3 of the present invention, the presence of Li in anatase type TiO ₂ was confirmed. Therefore, it was confirmed that TiO ₂ and LiTi ₂ O ₄ were present in the negative electrode layer after firing of the all solid state battery of the present invention.

<Evaluation of all solid state battery>
As shown in Table 2, from Examples 1 to 3 and Comparative Examples 1 and 2, the results of the electrochemical evaluation by the charge / discharge test, the X-ray diffraction measurement result, and the Li concentration analysis result by analytical electron microscope were used. The negative electrode layer of the all-solid-state battery manufactured in (1) includes anatase-type TiO ₂ and LiTi ₂ O ₄ pre-doped with Li derived from a glass electrolyte or a ceramic electrolyte before charging, that is, in a fully discharged state, and is subjected to an anatase type by a charging reaction. TiO ₂ changed to LiTi ₂ O ₄ , and after charging, the anatase-type cubic LiTi ₂ O ₄ was obtained. In the all solid state battery of the present invention, it was confirmed that the average operating voltage, the discharge capacity, and the energy density were improved by the presence of cubic LiTi ₂ O ₄ .

<Characteristic evaluation by half battery>
A half cell having a Li metal counter electrode was prepared and the charge / discharge characteristics of the negative electrode active material in the all solid state battery were evaluated. The half cell is composed of Li metal, a Li ion conductive polymer electrolyte layer, a solid electrolyte layer and a negative electrode layer. The Li ion conductive polymer electrolyte is ZEOSPAN8100 (trademark) (Nippon Zeon) and Li-TFSI (chemical formula (CF ₃ SO ₂ ) ₂ NLi), so that ZEOSPAN: Li-TFSI = 7.7: 2.3. After mixing and making a slurry with ethanol, the sheet was molded and dried.
The solid electrolyte layer and the negative electrode layer were produced by compacting powder and sintering after pressure molding.

The composition of the negative electrode layer is shown in Table 3, and the composition of the solid electrolyte layer is shown in Table 4.
The negative electrode layer and the solid electrolyte layer were prepared according to Tables 3 and 4, 100 g of YTZ balls (made by Nikkato) with a diameter of 5 mm were added, and the mixture was mixed for 5 minutes at 1000 rpm using a bubble taker Ryotaro (Sinky ARV-200). After cooling for 3 minutes for 3 minutes, the YTZ balls were separated and the solvent was removed by drying. What dried powder was made into the powder form with the laboratory miller was used for subsequent experiment.
After adding 30 mg of the negative electrode layer material mixed in a φ11 mm mold and adjusting the surface with a spatula and adjusting the surface with a pressing tool, 60 mg of the mixed solid electrolyte layer material was added and the surface adjusted with a spatula. Subsequently, after pressing at a pressure of 2000 kg / cm < ² >, it baked at 600 degreeC and the sintered compact was obtained. After lightly polishing the surface of the negative electrode layer and the surface of the solid electrolyte layer with No. 800 water-resistant abrasive paper, a copper foil for current collection was adhered to the negative electrode layer surface side using carbon paste and carbon paper, and a dry room with a dew point of −50 ° C. Inside, it baked at 150 degreeC for 1 hour.
After Li metal was pressure bonded to the copper foil, the Li ion conductive polymer electrolyte was used as a protective layer, and the Li ion conductive polymer electrolyte was pasted so that the solid electrolyte layer of the sintered body was in contact. The Li metal, the sintered body, and the lithium ion conductive polymer electrolyte were vacuum-packed with aluminum laminate packaging in a state where the copper foil was exposed to the outside so that it could be connected to an external terminal, and was cut off from the outside air.
The charge / discharge test was evaluated using a charge / discharge tester (ACD-M01A) manufactured by Asuka Electronics Co., Ltd., after CC charge at 17 μA, 1.2 V cutoff, and CC discharge at 3 V cutoff.
FIG. 8 shows the evaluation results with a half-cell. When Li ₄ Ti ₅ O ₁₂ was used as the negative electrode active material before firing, the charging potential decrease rate was faster than when TiO ₂ was used. In the discharge, when Li ₄ Ti ₅ O ₁₂ was used as the negative electrode active material, the average operating voltage was 41 mV lower than when TiO ₂ was used. It was confirmed that when Li ₄ Ti ₅ O ₁₂ was used as the negative electrode active material, it performed better as the negative electrode of the all-solid battery.

Table 3 Composition of negative electrode layer material used for half-cell

Table 4 Composition of solid electrolyte layer material used for half-cell

1: all-solid-state battery, 2: solid electrolyte layer, 3: positive electrode layer, 4: negative electrode layer.

Claims (6)

1. An all-solid battery including a solid electrolyte layer, a positive electrode layer, and a negative electrode layer,
   The solid electrolyte layer is interposed between the positive electrode layer and the negative electrode layer, and at least one of the positive electrode layer or the negative electrode layer and the solid electrolyte layer are bonded by baking,
   The solid electrolyte layer, the positive electrode layer, and the negative electrode layer all include a lithium ion conductive solid electrolyte,
   The negative electrode layer is as follows:
   (A) a negative electrode active material containing Li ₄ Ti ₅ O ₁₂ , TiO ₂ , or LiTi ₂ O ₄ ;
   (B) glass electrolyte and (c) ceramic electrolyte or glass ceramic electrolyte,
   An all solid state battery characterized in that it is obtained by sintering a material containing
2. The glass electrolyte comprises 10% by mass to 30% by mass of Li ₂ O component, more than 0% by mass to 12% by mass of Al ₂ O ₃ component, and 40% by mass to 90% by mass of P in terms of mass% based on oxide. _{2. The} composition according to claim 1, comprising ₂ O ₅ component and not including one or more selected from Y ₂ O ₃ component, Sc ₂ O ₃ component, ZrO ₂ component, CeO ₂ component and Sm ₂ O ₃ component. All solid battery.
3. The all-solid-state battery according to claim 1 or 2, wherein the negative electrode layer contains TiO ₂ and Li _x Ti ₂ O ₄ (x = 0 to 2) after firing and in a fully discharged state.
4. The all-solid-state battery according to any one of claims 1 to 3, wherein the negative electrode layer contains cubic Li _x Ti ₂ O ₄ (x = 0 more than 2) after charging.
5. An all-solid battery including a solid electrolyte layer, a positive electrode layer, and a negative electrode layer,
   The solid electrolyte layer is interposed between the positive electrode layer and the negative electrode layer, and at least one of the positive electrode layer or the negative electrode layer and the solid electrolyte layer are bonded by baking,
   The solid electrolyte layer, the positive electrode layer, and the negative electrode layer all include a lithium ion conductive solid electrolyte,
   The negative electrode layer is in a fully discharged state after firing,
   (A) TiO ₂ , and (b) Li _x Ti ₂ O ₄ (x = 0 more than 2)
   All-solid-state battery characterized by including.
6. 6. The all solid state battery according to claim 5, wherein the negative electrode layer contains cubic Li _x Ti ₂ O ₄ (x = 0 to 2) after charging.

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